/**
 * Calculates the percentage value of $px relatively to $px-context.
 * @param  {px value} $px          Part.
 * @param  {px value} $px-context  Context.
 * @return {% value}               Percentage value.
 */
@function px-to-pc($px, $px-context) {
  @return percentages($px / $px-context);
}